1. Field of the Invention
The present invention relates to an autofocus (hereinbelow, referred to as AF) image pickup apparatus provided with a distance measuring function having a parallax with respect to an image pickup optical system.
The present invention also relates to an AF lens apparatus which is detachable/attachable from/to a camera.
2. Description of the Related Art
Conventionally, as an autofocus technology, there has been used external distance measure type autofocus (external distance measuring AF), which employs infrared triangulation distance measurement or pupil division phase differential detection. With the external distance measuring AF, a distance can be measured directly, and thus a scanning operation or a hill-climbing operation is not required in determining the position of an in-focus point, which is necessary for video AF. Hence, the external distance measuring AF has a feature in which an in-focus state can be achieved at high speed. On the other hand, there are some drawbacks, such as a parallax which occurs between a taken image and a distance measuring area depending on an object distance, and the distance measuring area being fixed.
The following countermeasures have been proposed against such problems as described above, that is, the parallax and the limitation on the distance measuring area.
In order to overcome the parallax problem, Japanese Patent Application Laid-Open No. 2006-171290 discloses a technology of correcting a parallax by using the shake correction optical system provided to the image pickup optical system.
Japanese Patent Application Laid-Open No. 2006-119222 proposes the image pickup apparatus, which includes multiple object distance detectors and refers to the focal length of the zoom lens to calculate the object distance from the distance information obtained from the multiple object distance detectors. For each of the multiple object distance detectors, a different angle of view is determined so that the distance to an object can be measured (distance measuring) without being affected by the parallax in a given focal length range.
Japanese Patent Application Laid-Open No. H05-188280 discloses a technology of rotating the external distance measuring mechanism according to the angle of field for image taking so as to widen the distance measuring range.
Further, Japanese Patent Application Laid-Open No. H05-188280 proposes the camera which includes the driving unit for rotating the object distance detector and changes its rotation range according to the angle of field for image taking. However, in Japanese Patent Application Laid-Open No. 2006-171290, the optical axis direction of the image taking optical system is changed to correct the parallax, which is suitable for taking a still image, but there is no disclosure about an operation at the time of taking a moving image. In the technology disclosed in Japanese Patent Application Laid-Open No. 2006-119222, the multiple object distance detectors are provided and arranged by varying the angle of view. However, in order to suppress the influence of parallax in finely-divided focal length ranges, a large number of object distance detectors are necessary, resulting in complex configuration and control. In addition, there is no specific disclosure about its arrangement. Further, in Japanese Patent Application Laid-Open No. H05-188280, the distance to the object is measured in the entire angle of field for image taking, and accordingly, a camera operator cannot predict which position is to be focused in the image-taking range. This technology is suitable as the AF used when an ordinary camera operator takes an image. However, there is a problem that such technology is not practical as the AF used when a professional camera operator takes an image for the purpose of, for example, broadcasting, because the system does not allow the camera operator to perform the AF operation with respect to a position specified by the camera operator. In Japanese Patent Application Laid-Open No. H05-188280, the rotation range of the object distance detector is changed according to the angle of field for image taking. However, continuous distance measurement is performed in the angle of field for image taking, and hence it takes time to obtain distance measurement information.
In view of the above, an exemplary object of the present invention is to provide an optical apparatus capable of measuring a distance to an object with a wide focus area. The optical apparatus sets an angle between an optical axis of an image pickup optical system and an optical axis of an external distance measuring sensor appropriately according to a focal length of the image pickup optical system, shifts a distance measuring direction toward an AF execution position specified by an camera operator, and performs distance measurement with respect to the AF execution position, thereby performing an AF operation.